One of our favorite video makers, Afrotechmods, recently enabled Patreon. He mentioned that it takes hours for each minute of content produced. Bonkers. He has a great new set of videos out about switchmode power supplies.

Chris has been working on a new website for his day job. It is amazing how the mentality differs between hardware and software (especially web software). There is so much more license to change later (a big benefit, to be sure).

Chris also thought about how software people must feel when getting into hardware: they want it to be a one-click solution, just like how Chris wants WordPress (which we use on The Amp Hour) to “just work”.

Dave says this is the promise of modular hardware, which never really lives up to the hype. Chris thinks LittleBits is a good example of this: you can try lots of different things, but you would never differentiate in the marketplace without going custom (and losing the swappability)

2/ IBM is trying hard to sell off their fabs right now. Last offer they got was rumoured to be “pay us $2Bil and we will take those fabs off your hands” by GlobalFoundries, IBM was willing to only go as high as $1B. IBM cant even pay other people to take their fabs :o.

First lesson is about how easy it is to build something cool and working outright (instant gratification). I showed it to two kits (12 and 14) and they immediately went crazy for SDR. Starting with math would never work (and is standard in school, lets talk about sinus and cosinus for 3 weeks guys …been there), but they both know dB scale right now 😮 and cant wait for another lesson. At this point even some math wont be a problem, because they saw bigger picture (working radio), now they want to learn what makes it tick. This is such a game changer compared to my time in school (~15y ago), we used to do math in fundamental electronics class (book had 550 pages, walls of text and equations) it was simply retarded :/

Good point, I probably should have done it myself. The PFC circuit is actually controlled by the C2000 (as well as doing the motor control) and I wanted the ability to borrow that code later. And if I’m being completely honest, it scares the bejesus out of me 🙂 It’s not the 750W so much as the 350V.

Well, 350 V can’t make you any more dead than 180 V. (But it is probably more likely to do so.).

It sounds (from a few episodes) like you’re not very experienced with medium-sized power electronics. I hope you have a lot of fun learning about it.

I’m now going to be a concerned citizen / patronizing ass (delete whichever is inappropriate). The important things to remember are:
0) you don’t have to work on these higher voltages if you don’t want to!
1) like a gun is always loaded, an electrolytic cap is always charged. Hopefully TI put some bleed resistors in. If not, add some!
2) semi-permanently attach some kind of voltage indicator to the DC bus so you can check it’s dead before sticking your fingers in. An AC mains powered bench meter is my favorite.
3) if at all possible, discharge the DC link before moving your probes. Yes, it takes longer, but it’s easy to get shocked when you’re staring at the probe tip rather than your fingers. (I did this in February, quite embarrassing.)
4) if and when you shock yourself, do go to hospital. You can a) have a little heart attack or b) mess up your normal heart rhythms, go to bed and not wake up in the morning.
5) isolation is good. I suggest isolated programmers, comms leads and current probes. Differential scope voltage probes are also good.
6) as my old university lecturer says, ‘burning is learning.’
7) everybody loves novel-length comments!

I have worked on a 1200V DC bus before and scared myself with some bad . I’m just generally jittery around stuff that can kill me until I normalize to it. I’d say from a survival perspective, this is pretty smart! 🙂

In general, the TI kit is well thought out. Isolation on all the computer side stuff and some practical safety features. I could still kill myself with it, and they are sure to let me know as much, but I feel a little safer with this starting out than hacking an ATX power supply (plus the benefits of being able to borrow their OSHW design later).

Sorry if I came off as insluting or something, but I always figure it’s better to look bad than not tell someone something really important.

Anyhow, 1200 V can give you some good bang! And there’s always that feeling of danger when you get to the hard-power-on test. In June I had a particularly good one which actually blew the silicone gel out of the module :-), and that was only 800 V. How much bus capacitance did you have?

Maybe you and Dave should do a segment at some point on ‘best bangs.’ Err, actually, I just re-read that and it is perhaps not in keeping with the type content you and Dave normally provide ;-). Perhaps ‘best explosions?’

It was the power bus for the 6517B power supply. Pretty low power, but needed lots of caps for the voltage octupler. Could supply about 10 mA. One time I shorted +1200 to ground by accident, that is the time I really started respecting high voltage (though I thought I did prior to that).

Re: the sparkfun goof
They didn’t do everything right. They made a code change and didn’t run a full regression test. They just relied on production testings. No one ever plugged hardware with this new code on it in to a computer, yet they released it to production.

Watch any of Chris Tarnovsky’s talks from defcon/blackhat/etc if you want to see some incredible examples of reverse engineering chips by decapping them and mapping them out visually. I believe you will find it very interesting based on your comments about ken’s 7805. Goodspeed and Tarnovsky have blown my mind with their work, check it out.

Regarding non-unity power factor and the waveforms; The wikipedia link covers this but in the show I’d say Chris’s explanation rang a little more true. The voltage waveform will get distorted under heavy load with many types of loads. I’ve seen this effect. In school I was taught the phase angle idea but in practice the current waveform is often very complicated and not at all close to sinusoidal (one more way school failed to teach real engineering). The Voltage waveform can be distorted so it is better to use the calculation: power factor = real power / apparent power.

As Dave said, the regular residential customer does not pay for apparent power, we pay for real power.